Apparatus And Methods For Converting A Cryogenic Fluid Into Gas

ABSTRACT

Method and apparatus for vaporizing cryogenic fluids in which an intermediate heat transfer fluid is first heated across a heat transfer surface with ambient air, and then the heat transfer surface provides heat to vaporize the cryogenic fluid.

BACKGROUND OF THE INVENTION

The present invention relates to cryogenic fluids. In another aspect,the present invention relates to apparatus and methods for processing,transporting and/or storing cryogenic fluids. In even another aspect,the present invention relates to apparatus and methods for converting acryogenic fluid into a gas. In even another aspect, the presentinvention relates to methods and apparatus for processing, transportingand/or storing liquified natural gas (“LNG”). In still another aspect,the present invention relates to apparatus and methods for modifyingand/or retrofitting cryogenic vaporization systems.

Most conveniently, natural gas is transported via pipeline from thelocation where it is produced to the location where it is consumed.However, given certain barriers of geography, economics, and/orpolitics, transportation by pipeline is not always possible, economic orpermitted. Without an effective way to transport the natural gas to alocation where there is a commercial demand, the gas may be burned as itis produced, which is wasteful.

Liquefaction of the natural gas facilitates storage and transportationof the natural gas (a mixture of hydrocarbons, typically 65 to 99percent methane, with smaller amounts of ethane, propane and butane).When natural gas is chilled to below its boiling point (in theneighborhood of −260 F depending upon the composition) it becomes anodorless, colorless liquid having a volume which is less than one sixhundredth ( 1/600) of its volume at ambient atmospheric surfacetemperature and pressure. Thus, it will be appreciated that a 150,000cubic meter LNG tanker ship is capable of carrying the equivalent of 3.2billion cubic feet of natural gas.

It is not uncommon for natural gas to be produced in remote locations,such as Algeria, Borneo, or Indonesia, and then liquefied and shippedoverseas in this manner to Europe, Japan, or the United States.Typically, the natural gas is gathered through one or more pipelines toa land-based liquefaction facility. The LNG is then loaded onto a tankerequipped with cryogenic compartments (such a tanker may be referred toas an LNG carrier or (“LNGC”) by pumping it through a relatively shortpipeline. After the LNGC reaches the destination port, the LNG isoffloaded by cryogenic pump to a land-based regasification facility,where it may be stored in a liquid state or regasified. If regasified,the resulting natural gas then may be distributed through a pipelinesystem to various locations where it is consumed.

In many circumstances, hot water or steam is used to heat the liquefiedgas for vaporization. Unfortunately, such hot water or steam oftenfreezes so as to give rise to the hazard of clogging up the evaporator.Various improvements in this process have heretofore been made. Theevaporators presently used are mainly of the open rack type,intermediate fluid type and submerged combustion type.

Open rack type evaporators use sea water as a heat source for thevaporization of liquefied natural gas. These evaporators useonce-through seawater flow on the outside of a heat exchanger as thesource of heat for the vaporization. They do not block up from freezingwater, are easy to operate and maintain, but they are expensive tobuild. They are widely used in Japan. Their use in the USA and Europe islimited and economically difficult to justify for several reasons. Firstthe present permitting environment does not allow returning the seawaterto the sea at a very cold temperature because of environmental concernsfor marine life. The present permitting environment allows only a smalldecrease in temperature before returning the seawater back to the sea,which would require a very large sea water quantity to be pumped throughthe system, if the terminal vaporization capacity was designed for acommercial size as economics would require. Also coastal waters likethose of the southern USA are often not clean and contain a lot ofsuspended solids, which could require filtration. In addition the seawater intake structure would have to be located far away from theevaporators in most cases because of location restraints or to get todeep and clean sea water at the intake. With these restraints the use ofopen rack type vaporizers in the USA is environmentally and economicallynot feasible.

Instead of vaporizing liquefied natural gas by direct heating with wateror steam, evaporators of the intermediate fluid type use propane,fluorinated hydrocarbons or like refrigerant having a low freezingpoint. The refrigerant is heated with hot water or steam first toutilize the evaporation and condensation of the refrigerant for thevaporization of liquefied natural gas. Evaporators of this type are lessexpensive to build than those of the open rack-type but require heatingmeans, such as a burner, for the preparation of hot water or steam andare therefore costly to operate due to fuel consumption.

Evaporators of the submerged combustion type comprise a tube immersed inwater which is heated with a combustion gas injected thereinto from aburner. Like the intermediate fluid type, the evaporators of thesubmerged combustion type involve a fuel cost and are expensive tooperate.

The patent art is replete with a number of patents directed to processesand apparatus for the vaporization of liquefied natural gas.

For example, U.S. Pat. No. 4,170,115, issued on Oct. 9, 1979 to Ooka etal., describes an apparatus for vaporizing liquefied natural gas usingestuarine water. This system is arranged in a series of heat exchangersof the indirect heating, intermediate fluid type. A multitubularconcurrent heat exchanger is also utilized in conjunction with amultitubular countercurrent heat exchanger. As a result, salt water isused for the vaporization process. U.S. Pat. No. 4,224,802, issued onSep. 30, 1980 to the same inventor, describes a variation on this typeand also uses estuarine water in a multitubular heat exchanger.

U.S. Pat. No. 4,331,129, issued on May 25, 1982 to Hong et al., teachesthe utilization of solar energy for LNG vaporization. The solar energyis used for heating a second fluid, such as water. This second fluid ispassed into heat exchange relationship with the liquefied natural gas.The water contains a anti-freeze additive so as to prevent freezing ofthe water during the vaporization process.

U.S. Pat. No. 4,399,660, issued on Aug. 23, 1983 to Vogler, Jr. et al.,describes an atmospheric vaporizer suitable for vaporizing cryogenicliquids on a continuous basis. This device employs heat absorbed fromthe ambient air. At least three substantially vertical passes are pipedtogether. Each pass includes a center tube with a plurality of finssubstantially equally spaced around the tube.

U.S. Pat. No. 5,251,452, issued on Oct. 12, 1993 to L. Z. Widder, alsodiscloses an ambient air vaporizer and heater for cryogenic liquids.This apparatus utilizes a plurality of vertically mounted and parallellyconnected heat exchange tubes. Each tube has a plurality of externalfins and a plurality of internal peripheral passageways symmetricallyarranged in fluid communication with a central opening. A solid barextends within the central opening for a predetermined length of eachtube to increase the rate of heat transfer between the cryogenic fluidin its vapor phase and the ambient air. The fluid is raised from itsboiling point at the bottom of the tubes to a temperature at the topsuitable for manufacturing and other operations.

U.S. Pat. No. 5,819,542, issued on Oct. 13, 1998 to Christiansen et al.,teaches a heat exchange device having a first heat exchanger forevaporation of LNG and a second heat exchanger for superheating ofgaseous natural gas. The heat exchangers are arranged for heating thesefluids by means of a heating medium and having an outlet which isconnected to a mixing device for mixing the heated fluids with thecorresponding unheated fluids. The heat exchangers comprise a commonhousing in which they are provided with separate passages for thefluids. The mixing device, constitutes a unit together with the housingand has a single mixing chamber with one single fluid outlet. Inseparate passages, there are provided valves for the supply of LNG inthe housing and in the mixing chamber.

U.S. Pat. No. 6,622,492, issued Sep. 23, 2003, to Eyermann, disclosesapparatus and process for vaporizing liquefied natural gas including theextraction of heat from ambient air to heat circulating water. The heatexchange process includes a heat exchanger for the vaporization ofliquefied natural gas, a circulating water system, and a water towerextracting heat from the ambient air to heat the circulating water. Tomake the process work throughout the year the process may besupplemented by a submerged fired heater connected to the water towerbasin.

U.S. Pat. No. 6,644,041, issued Nov. 11, 2003 to Eyermann, discloses aprocess for vaporizing liquefied natural gas including passing waterinto a water tower so as to elevate a temperature of the water, pumpingthe elevated temperature water through a first heat exchanger, passing acirculating fluid through the first heat exchanger so as to transferheat from the elevated temperature water into the circulating fluid,passing the liquefied natural gas into a second heat exchanger, pumpingthe heated circulating fluid from the first heat exchanger into thesecond heat exchanger so as to transfer heat from the circulating fluidto the liquefied natural gas, and discharging vaporized natural gas fromthe second heat exchanger.

In spite of the advancements of the prior art, there is still a need inthe art for improved apparatus and methods for processing, transporting,and/or storing LNG.

There is another need in the art for apparatus and methods forconverting a liquefied cryogenic fluid into a gas.

There is even another need in the art for apparatus and methods forconverting a liquified natural gas into gaseous natural gas.

This and other needs in the art will become apparent to those of skillin the art upon review of this specification, including its drawings andclaims.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for improvedapparatus and methods for processing, transporting, and/or storing LNG.

It is another object of the present invention to provide for apparatusand methods for converting a liquified cryogenic fluid into a gas.

It is even another object of the present invention to provide forapparatus and methods for converting a liquified natural gas intogaseous natural gas.

This and other objects of the present invention will become apparent tothose of skill in the art upon review of this specification, includingits drawings and claims.

According to one embodiment of the present invention, there is provideda method of vaporizing a cryogenic fluid. The method includes providingheat from ambient air to a heat transfer fluid across a heat transfersurface, wherein the ambient air and heat transfer fluid are not indirect contact. The method also includes providing heat from the heattransfer fluid to a cryogenic fluid sufficient to vaporize the cryogenicfluid.

According to another embodiment of the present invention, there isprovided an apparatus for vaporizing a cryogenic fluid. The apparatuscomprises a heat transfer fluid closed circulation loop defined by anambient air heat exchanger, a heater and a vaporizer; and an LNG flowpath defined thru the vaporizer.

According to even another embodiment of the present invention, there isprovided a method of modifying a vaporizing system in which a heattransfer fluid is circulated thru a heater to heat up the fluid and thencirculated thru a vaporizer to vaporize the cryogenic fluid. The methodincludes the addition of a ambient air heat exchanger to provide heat tothe heat exchange fluid.

According to still another embodiment of the present invention, there isprovided a modified system for vaporizing a cryogenic fluid comprising aheat transfer fluid heater and vaporizer, and comprising an ambient airheat exchanger added after the heat transfer fluid heater and vaporizerhave been in operation in the system.

These and other embodiments of the present invention will becomeapparent to those of skill in the art upon review of this specification,including its drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, it should be understood that like reference numbersrefer to like members.

FIG. 1 is a process flow schematic showing regasification system 100having air exchange pre-heater 101, economizer 103, heater 105, waterknockout 111, vaporizer 114, produced water pump 117, circulating fluidsurge tank 119, and circulating fluid pump 121.

FIG. 2 is a process flow schematic showing regasification system 200having tube-in-tube air exchanger 201, economizer 203, vaporizer 214,produced water knockout 211, produced water pump 217, warming mediumaccumulator 219 and warming medium pump 221.

FIGS. 3 and 4 are schematics showing a retrofit of a typical ethyleneglycol LNG vaporization system 300 having heater 302, LNG vaporizer 301,accumulator 303, and circulation pump 307.

FIG. 5 is a schematic showing a retrofit of a water bath or submergedcombustion system.

FIGS. 6 and 7 are schematics showing a retrofit of a typical coolingtower vaporization system 400, having cooling tower 401, pump 403,exchanger 404, tank 405, LNG vaporizer 406, pump 407 and submerged bathheater 408.

FIG. 8 is a process flow schematic showing vaporization process system800 having air exchange pre-heater 801, accumulator 804, auxiliaryheater 805, vaporizer 814, air exchange feeder line valve 816, heaterfeeder line valve 818 and temperature controller 825.

FIG. 9 is a process flow schematic showing vaporization process system900 having air exchange pre-heater 901, auxiliary heater vaporizer 903,cold separator 904, auxiliary heater 905, second fluid pump 910,pre-heater vaporizer 914, pre-heater vaporizer LNG feed valve 916,auxiliary heater vaporizer LNG feed valve 918, second air exchangeheater 920 and temperature controller 925.

DETAILED DESCRIPTION OF THE INVENTION

While some descriptions of the present invention may make reference toliquified natural gas (“LNG”), it should be understood that the presentinvention is not limited to utility with LNG, but rather has broadutility with cryogenic fluids in general, preferably cryogenic fluidsformed from flammable gases.

The apparatus of the present invention will find utility for processing,storing, and/or transporting (i.e., including but not limited to,receiving, dispensing, distributing, moving) cryogenic fluids, anon-limiting example of which is liquified natural gas (“LNG”). Morespecifically,the present invention provides apparatus and methods forconverting a cryogenic fluid into a gas, which apparatus and methods maybe used not along in a stand alone manner, but which may also beutilized with and/or incorporated into apparatus and methods forprocessing, storing, and/or transporting cryogenic fluids.

According to the present invention, there is an unexpected advantageobtained using a standard air cooler as a heater while passing a fluidthrough the tubes to pick up heat from the air, preferable on acontinuous basis. While ambient vaporizers have been used to heat LNG,but require alternating between a number of units as they freeze up fromwater vapor in the air. The present invention employs an intermediateheat transfer fluid and selected temperatures, wherein frost does notinhibit the transfer surface, to vaporize LNG.

A first non-limiting embodiment of the apparatus and methods of thepresent invention is best described by reference to FIG. 1, a processflow schematic showing regasification system 100 having air exchangepre-heater 101, economizer 103, heater 105, water knockout 111,vaporizer 114, produced water pump 117, circulating fluid surge tank119, and circulating fluid pump 121.

LNG is provided to vaporizer 114 via piping 21 at around −252 F, andexits vaporizer 114 via piping 22 as gaseous natural gas at about 40 F.A circulating heat transfer fluid is provided to vaporizer 114 viapiping 31, and exits vaporizer 114 via piping 32 as a cooled heattransfer fluid.

Heat transfer fluids suitable for use in the present invention includehydrocarbons, non-limiting examples of which include propane and butane,ammonia, glycol-water mixtures, formate-water mixtures, methanol,propanol, and other suitable heat transfer fluids as may be useful underthe operating conditions.

The heat transfer fluid is circulated in a closed system through airexchange pre-heater 101 where it is first heated after being cooled invaporizer 114, then through economizer 103/heater 105 where it may befurther heated if necessary, then through vaporizer 114 where it isutilized to provide heat of vaporization to the LNG, before returning topre-heater 101. This heat transfer circulation system may be providedwith one or more surge tanks 119 as necessary. Circulation of the heattransfer fluid is maintained by one or more circulation pumps 121. Anitrogen line 51 and pressure controller 55 maintain pressure of theheat transfer circulation system as desired.

In the practice of the present invention, heat is provided from ambientair to the heat transfer fluid across a heat transfer surface ratherthan by direct contact between the ambient air and heat transfer fluid.For example, the heat transfer fluid is passed through the tubes of aheat exchanger while the ambient air passes through the shell side.

Under certain conditions (see Examples 1, 2 and 3 below), ambient airwill provide all of the heating necessary without the need for theeconomizer 103/heater 105 providing any: heating duty.

When heater 105 is necessary it will be most efficiently run inconjunction with economizer 103, in which the exit effluent from heater105 routed to economizer 103 to heat the LNG or other cryogenic fluid.The cooled effluent exits economizer 103 and flows to water knockouttank 111. Pump 117 eliminates produced water from the system.

A second non-limiting embodiment of the apparatus and methods of thepresent invention is best described by reference to FIG. 2, which is aprocess flow schematic showing regasification system 200 havingtube-in-tube air exchanger 201, economizer 203, vaporizer 214, producedwater knockout 211, produced water pump 217, warming medium accumulator219 and warming medium pump 221.

In this embodiment, heat exchanger 201 is a tube-in-tube air exchanger(i.e, two tubes arranged in a concentric fashion), in which thecryogenic fluid passes through the inner most tube, pump 221 circulatesthe heat transfer fluid through the annular space between the two tubes,and ambient air passes over the surface of the outer tube. Accumulator219 provides volume to the system to aid in heat transfer. For thosetimes when the ambient air is too cool, extra heating may be provided byheater 214/economizer 203. Hot exit effluent from heater 214 routed toeconomizer 203 to heat the LNG or other cryogenic fluid. The cooledeffluent exits economizer 203 and flows to water knockout tank 211. Pump217 eliminates produced water from the system.

The methods and apparatus of the present invention also provide forretrofitting of pre-existing cryogenic regassification apparatus.

In its simplest aspect, regassification which involves closed loopcirculation of a heat transfer fluid thru a heater and then into avaporizer to heat and vaporize a cryogenic fluid, may be modified byplacing an ambient air heat exchanger ahead of the heater to eitherpre-heat or fully heat the heat transfer fluid. Of course, there willnot be direct contact of the heat transfer fluid with the ambient air,but rather indirect contact across a heat transfer service.

For example, referring now to FIG. 3, there is shown a retrofit of atypical ethylene glycol LNG vaporization system 300 having heater 302,LNG vaporizer 301, accumulator 303, and circulation pump 307. In amethod of retrofitting/modifying the system to form aretrofitted/modified system, air pre-heater 315 is added just upstreamof heater 302 to serve as a pre-heater and/or heater.

Referring now to FIG. 6, there is shown a retrofit of a typical coolingtower vaporization system 400, having cooling tower 401, pump 403,exchanger 404, tank 405, LNG vaporizer 406, pump 407 and submerged bathheater 408. In a method of retrofitting/modifying the system to form aretrofitted/modified system, air pre-heater 415 is added. However,instead of preheating the LNG, this heater 415 serves to heat the heattransfer fluid flowing through vaporizer 406.

More complex modification/retrofitting of such existing systems involvetaking a side stream of the cryogenic fluid and routing it thru avaporizer in which the vaporizer heat transfer fluid has been heated byambient air in the manner of the present invention. Essentially, such aretrofit is the addition of the apparatus and method of the presentinvention to handle at least a portion of the vaporization.

For example, the typical ethylene glycol/water system shown in FIG. 3and modified/retrofitted by the addition of air pre-heater 315, mayinstead be modified/retrofitted as shown in FIG. 4 by the addition ofsystem 500 in which a heat transfer fluid is circulated in a closedcircuit via pump 505 through air heater 502 where it is heated, throughexchanger 501 where it heats LNG, through accumulator 503, and back toheater 502 to complete the circuit. Controller 509 regulates flow of LNGto the pipeline and/or back to the LNG Vaporizer.

As another example, the typical cooling tower vaporization system shownin FIG. 6 and modified/retrofitted by the addition of air exchanger 415,may instead be modified/retrofitted as shown in FIG. 7 by the additionof system 500 in which a heat transfer fluid is circulated in a closedcircuit via pump 505 through air heater 502 where it is heated, throughexchanger 501 where it heats LNG, through accumulator 503, and back toheater 502 to complete the circuit. Controller 509 regulates flow of LNGto the pipeline and/or back to the LNG Vaporizer.

FIG. 5 is a schematic showing the retrofit of a water bath or submergedcombustion vaporizer by the addition of system 500 as described above.

Another non-limiting embodiment of the apparatus and methods of thepresent invention is best described by reference to FIG. 8, which is aprocess flow schematic showing vaporization process system 800 havingair exchange pre-heater 801, accumulator 804, auxiliary heater 805,vaporizer 814, air exchange feeder line valve 816, heater feeder linevalve 818 and temperature controller 825.

In this embodiment, temperature controller 825 monitors the temperatureof the heat transfer fluid. If the temperature of the heat transferfluid is not sufficiently high, then controller 825 operates valves 816and 818 to achieve a desired heat transfer fluid temperature, byutilizing pre-heater 801, auxiliary heater 805, or a combination thereofwith the heating duty shared between heaters 801 and 805 in any suitableratio. Controller 825 can be equipped with suitable algorithms in theform of either software and/or hardware to carry out this temperaturecontrol.

Another embodiment of the present invention is shown in FIG. 9, which isa process flow schematic showing vaporization process system 900 havingair exchange pre-heater 901, auxiliary heater vaporizer 903, coldseparator 904, auxiliary heater 905, second fluid pump 910, pre-heatervaporizer 914, pre-heater vaporizer LNG feed valve 916, auxiliary heatervaporizer LNG feed valve 918, second air exchange heater 920 andtemperature controller 925.

This embodiment contains a pair of vaporizers in which vaporizer 903receives heat transfer liquid from heater 905 and the other vaporizer914 receives heat from heater 901. Temperature controller 925 monitorsthe temperature of gas 930 and operates valves 916 and 918 according toan algorithm to achieve the desired temperature of gas 930. Thevaporization load is carried by the auxiliary heater vaporizer 903 andpre-heater vaporizer 914, or a combination thereof with the vaporizationload shared between vaporizers 903 and 914 in any suitable ratio.

It should be understood that any of the above systems may incorporateprocess controls/methods as are known to those of skill in the art. Forexample, by-passes around any of the heat exchanges may be utilized. Itshould also be understood that much of the micro engineering/processdetail is not shown in the above illustrations but would be well withinthe knowledge and understanding of those of skill in the art.

EXAMPLES

The following non-limiting examples are provided merely to illustrate afew embodiments of the present invention, and there examples are notmeant to and do not limit the scope of the claims of the presentinvention. These inventions are theoretical calculated examples.

Example 1

This example utilizes the apparatus and method as shown in FIG. 1 (11 at−10 F, 31 at 50 F, 32 at −10 F, and 1 19 at 16 psig). The cryogenicfluid is a typical LNG. The circulating fluid utilized is propane. Theduty percentage for the air cooler 101, and the combined duty percentagefor fired heater 105 and economizer 103 were calculated for ambient airtemperatures of 35 F, 45 F, 65 F, 70 F and 85 F, with these percentagespresented in the following TABLE 1. The propane circulation is about 1.7lb propane/lb LNG, with the rate depending upon the temperature andpressure of the LNG and propane. The propane circulation range isestimated to be from about 1.0 to 2.5 lb propane/lb LNG. TABLE 1 DutyPercentage at Various Ambient Air Temperatures 85 F. 70 F. 65 F. 45 F.35 F. Air Cooler 100 100 95 70 58 Fired Heat/Economizer 0 0 5 30 42Total 100 100 100 100 100

Example 2

This example also utilizes the apparatus and method as shown in FIG. 1(1 @ −10 F, 31 @ 50 F, 32 @ −10 F, and 119 at 100 psig). The cryogenicfluid is again a typical LNG. The circulating fluid utilized is propane.The duty percentage for the air cooler 101, and the combined dutypercentage for fired heater 105 and economizer 103 were calculated forambient air temperatures of 35 F, 45 F, 65 F, 70 F and 85 F, with thesepercentages presented in the following TABLE 2. The propane circulationis about 7.6 lb propane/lb LNG, with the rate depending upon thetemperature and pressure of the LNG and propane. The propane circulationrange is estimated to be from about 5.0 to 10.0 lb propane/lb LNG. TABLE2 Duty Percentage at Various Ambient Air Temperatures 85 F. 70 F. 65 F.45 F. 35 F. Air Cooler 100 100 93 57 47 Fired Heat/Economizer 0 0 7 4353 Total 100 100 100 100 100

Example 3

This example again utilizes the apparatus and method as shown in FIG. 1(11 at range of −10 F to 30 F, 30 at −10 F, 31 at 50 F, 32 at 30 F, and119 at 16 psig). The cryogenic fluid is a typical LNG. Rather than usingpropane as the circulating fluid, WBF is utilized. As with Examples 1and 2, the duty percentage for the air cooler 101, and the combined dutypercentage for fired heater 105 and economizer 103 were calculated forambient air temperatures of 35 F, 45 F, 65 F, 70 F and 85 F, with thesepercentages presented in the following TABLE 3. The WBF circulation isabout 10-30 lb WBF/lb LNG, with the rate depending upon the temperatureand pressure of the LNG and propane. TABLE 3 Duty Percentage at VariousAmbient Air Temperatures 85 F. 70 F. 65 F. 45 F. 35 F. Air Cooler 100100 93 60 51 Fired Heat/Economizer 0 0 7 40 49 Total 100 100 100 100 100

Example 4

This example utilizes the apparatus and method as shown in FIG. 2. Thecryogenic fluid is a typical LNG. The warming medium utilized ispropane. The duty percentage for the tube-in-tube air exchange 201, andthe combined duty percentage for fired heater 214 and economizer 203were calculated for ambient air temperatures of 35 F, 45 F, 65 F, 70 Fand 85 F, with these percentages presented in the following TABLE 4. Theeconomizer is used with the Water Bath Heater only. TABLE 4 DutyPercentage at Various Ambient Air Temperatures 85 F. 70 F. 65 F. 45 F.35 F. Air Cooler 100 100 93 57 47 Fired Heat/Economizer 0 0 5 43 53Total 100 100 100 100 100

Example 5

Potential savings utilizing present invention.

Basis: 1000 MMBtu/Hr; Air exchanger designed assuming 70 F; $5.00/MMBtu;365 days of operation/yr.

Month: Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

T(F): 51 54 61 67 75 81 82 83 79 70 61 55

AIR Htr % Duty: 77.5 81 90 94 100 100 100 100 100 100 90 80

Air Duty

(MMBtu/Hr): 775 810 900 940 1000 1000 1000 1000 1000 1000 900 800

Average Yearly Savings:927.1×$5×24×365=$40.6 MM/Yr.

The above calculations are based on approximately 1500 MMSCFD beingvaporized.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present invention,including all features which would be treated as equivalents thereof bythose skilled in the art to which this invention pertains.

1. A method of vaporizing a cryogenic fluid, the method comprising thesteps of: providing heat from ambient air to a heat transfer fluidacross a heat transfer surface, wherein the ambient air and heattransfer fluid are not in direct contact; providing heat from the heattransfer fluid to a cryogenic fluid sufficient to vaporize the cryogenicfluid.
 2. The method of claim 1, wherein the cryogenic fluid is LNG. 3.An apparatus for vaporizing a cryogenic fluid, comprising: a heattransfer fluid closed circulation loop defined by an ambient air heatexchanger, a heater and a vaporizer; and an LNG flow path defined thruthe vaporizer.
 4. A method of modifying a vaporizing system in which aheat transfer fluid is circulated thru a heater to heat up the fluid andthen circulated thru a vaporizer to vaporize the cryogenic fluid, themethod comprises addition of a ambient air heat exchanger to provideheat to the heat exchange fluid.
 5. A modified system for vaporizing acryogenic fluid comprising a heat transfer fluid heater and vaporizer,and comprising an ambient air heat exchanger added after the heattransfer fluid heater and vaporizer have been in operation in thesystem.